Basically, a hearing aid has a microphone for converting sound into an electric signal, an amplifier for alleviating the hearing loss of the user and a receiver for converting the amplified electric signal into sound again. Modern, digital hearing aids comprise sophisticated and complex signal processing units for processing and amplifying sound according to a prescription aimed at alleviating a hearing loss for a hearing impaired individual. The major purpose of a hearing aid is to improve speech intelligibility.
State of art hearing aids have features for recognizing speech and suppressing noise in an audio signal picked up by the hearing aid. A useful element in the statistical analyses is percentile levels. Hearing aids are able to assume various modes in dependence of the detected sound environment, and when music is included in the background noise, the microphone assembly of the hearing aid may become directional in order to suppress noise from offset directions.